The sorting of sawn packages on tape is one of the key back-end processes for the manufacture of electronic packages like Chip-Scale Packages (“CSP”) when a tape sawing method is adopted. A CSP semiconductor package comprises a lead or ball side for making electrical connections with other devices, as well as a mold side comprising an encapsulant for protecting the internal circuitry. The mold side is also commonly referred to as a marking side as labels or other information may be marked onto this surface of the package. Inspection results on the lead/ball side and mold/marking side is a common criteria used when sorting different packages that have been formed to determine whether packages have been satisfactorily assembled. Therefore, an important performance index for a machine processing CSP packages is its inspection and sorting throughput.
Typically, current sorting systems employ one of two methods. The first method is to align the sawn packages on an adhesive mounting tape with the balls or leads facing away from the tape, and inspect the balls or leads on the packages. The sawn packages are then picked up from the mounting tape with a pick head. Then, the pick head moves to a position where a mold/mark side inspection optics system is positioned to inspect the mold/marked sides of picked packages. After that, good packages are offloaded to a container, such as a tray or tube container, and rejected packages are disposed of in a reject bin. Further, reworked units may be transferred to another tray or bin.
Using this first method, it is difficult to avoid sequential operations involving package alignment on tape, lead or ball side inspection and finally mold or marking side inspection. The result is long cycle time and low throughput. In order to accommodate such operations in sequence, a long traveling distance is common for this method, and therefore the cycle time is further increased. A common way to shorten the cycle time is to provide multiple pick heads (for example, four to ten pick heads) mounted on transfer arms. The drawback of this approach is that the loading and complexity of the arm is increased, and it necessitates a longer conversion time from processing one package size to another as the suction pads of pick heads have to keep changing when the package sizes vary a lot.
The second method involves picking up sawn packages mounted on an adhesive mounting tape using pick heads attached to a turret. Each turret usually comprises more than eight pick heads. The picked packages are placed onto a turntable including holders where ball or lead side inspection will be performed, A second turret with pick heads (again, with usually more than eight pick heads) picks up the packages from the turntable. The mold/mark sides of the picked packages are then inspected at another location along the rotating path of the pick heads of the turret. Thereafter, packages are offloaded to different containers according to quality
This second method involves a relatively complex design. Long alignment and machine setup time is incurred as two turrets and one turntable of numerous pick heads have to be aligned. There is also increased conversion time since the many pick heads of the two turrets and holders of the turntable have to be changed if package sizes vary frequently. For the same reason, the conversion kit would be more expensive.
After pick-up, inspection and/or other checking processes, the packages have to be sorted and offloaded to an offloading system. Usually, there are two types of offloading methods, namely offloading to tray and offloading to tube. The good packages are put into trays, tubes or other offloading formats. The reworked packages will usually be put into trays or reworked bins, while the rejected packages are put into reject bins. Usually, for packages of larger sizes (say, 6 mm×6 mm or larger), trays are preferred as the offloading format for good and reworked packages. For smaller packages, (say, 5 mm×5 mm or smaller), the tube offload format is usually preferred for good packages, while the bin format is selected for reworked and rejected packages. Therefore, the offload configuration required may often vary from one user to another and it would be desirable to provide more than one offloading format for a user.
In prior art systems, the configurability of the offloading systems are not flexible enough. Frequently, the offloading configuration has to be determined before the machine is built, and once built, a change of offloading configuration is very difficult if not impossible. As a result, the production lead-time is long.
Furthermore, due to this inflexibility, the offload configuration may only be suitable for one type of packages, For example, a tray-tray-tube configuration may be made to handle large packages such that the third tube offload format is treated as a spare for future use. In case smaller packages that are only suitable for tube offload are used, the offloading cycle time will be longer, since the traveling distance and time is longer and there is no option of repositioning the tube offload nearer to the packages being offloaded.